1. Field of the Invention
The present invention relates to a printing unit arrangement in a web-fed rotary printing press. In particular, the present invention relates to a printing unit arrangement in a lithographic web-fed rotary printing press which allows to print a 4/4 image on both sides of a paper web and which also allows for edition changes while the printing press is in operation.
2. State of the Art
In a lithographic web-fed rotary printing press, a running paper web is usually fed through a plurality of blanket-to-blanket printing units, which apply a multicolor image to both sides of the web. For driving the printing units, different drive systems, drive principles and configurations of drive motors and drive gears are known from the prior art.
One of the most common driving principles used in combination with blanket-to-blanket printing units uses one single drive motor per printing unit, in order to drive the couples of associated plate and blanket cylinders which are mechanically coupled via meshing drive gear wheels. Although this principle is the most cost effective principle, the coupling of the plate and blanket cylinders via meshing gear wheels does not allow for flying imprinter operations which are necessary for edition changes and changes of spot colors in the printed image, while the printing press is in operation. Accordingly, these printing units do not offer a high flexibility and also require a shutdown of the printing presses for a comparatively long time, in order to exchange printing plates and/or the printing units in case of an edition change.
U.S. Pat. No. 6,032,579 describes a blanket-to-blanket printing unit for a lithographic web-fed rotary newspaper printing press, in which the two blanket cylinders are mechanically coupled via drive gears which are driven by a first drive motor. Each of the two plate cylinders associated with one of the blanket cylinders is driven by its own independent drive motor, respectively. Due to the simultaneous control of the three independent drive motors, this highly flexible printing unit requires a sophisticated and therefore costly and complex control system.
EP 0 820 861 A2 purports to disclose a blanket-to-blanket printing unit, in which the two blanket cylinders and one of the plate cylinders can be mechanically coupled to each other to be driven by a first drive motor, whereas the second plate cylinder is separately driven by a second drive motor, in order to perform a flying imprinter operation on one side of the web. In order to perform a flying imprinter operation on the other side of the web the drive gear wheel associated with the first drive motor can be brought out of mesh with the gear wheels of the blanket cylinders, and a further gear wheel coupled to the drive shaft of the second drive motor can be brought into mesh with the blanket cylinder drive gear wheels.
Due to the movable drive gear wheels, the print quality which can be obtained with the above-described printing unit is rather low compared to printing units, in which the drive gear wheels of the printing unit cylinders are in a constant mesh. Moreover, the document does not give any teaching to use the described 2-motor-drive printing unit in combination with other printing units in a tower arrangement.
Having outlined the state of the art and its attendant disadvantages, it is accordingly an object of the present invention, to provide for a printing unit arrangement in a lithographic web-fed rotary printing press for printing newspapers, which on the one hand allows for flying imprinter operations, and which on the other hand requires a reduced number of drive motors for driving the printing unit arrangement.
According to a first object of the present invention, a printing unit arrangement in a web-fed rotary printing press comprises a first printing unit including a first and a second plate cylinder and a first and a second blanket cylinder. The first and second blanket cylinders and first and second plate cylinders are mechanically coupled to each other and are commonly driven by a common drive motor. The arrangement further comprises a second printing unit which includes a first plate cylinder, a first blanket cylinder associated with the first plate cylinder, a second blanket cylinder mechanically coupled to the first blanket cylinder and a second plate cylinder associated with and being mechanically coupled to the second blanket cylinder, a first drive motor for individually driving the first plate cylinder and a second drive motor for commonly driving the first and second blanket cylinders and the second plate cylinder. The first and second printing units are arranged to print a colored image on both sides of a running paper web. This embodiment of the invention has the advantage that the second printing unit for performing the flying imprinter operation only uses two drive motors, which require a simplified and much more cost effective control equipment, whereas it allows at the same time for high quality printing, due to the fixed mechanical coupling of the two blanket cylinders and the associated plate cylinder.
According to another object of the present invention, a print unit arrangement in a web-fed rotary printing press comprises a third printing unit, which includes a first plate cylinder, a first blanket cylinder associated with said first plate cylinder, a second blanket cylinder mechanically coupled to said first blanket cylinder and a second plate cylinder associated with and being mechanically coupled to said second blanket cylinder, a first drive motor for individually driving said first plate cylinder and a second drive motor for commonly driving said first and second blanket cylinders and said second plate cylinder. The first plate cylinder of the second printing unit and the first plate cylinder of the third printing unit are engageable and disengageable with their associated blanket cylinders in alternation, in order to perform a flying imprinter operation on the same side of the web.
According to an even further object of the present invention, the printing unit arrangement in a web-fed rotary printing press comprises a first printing unit, which includes a first and a second plate cylinder and a first and a second blanket cylinder. The first and second blanket cylinders and first and second plate cylinders are mechanically coupled to each other and are commonly driven by a common drive motor. Moreover, the arrangement comprises a second printing unit, including a first plate cylinder, a first blanket cylinder associated with the first plate cylinder, a second plate cylinder, a second blanket cylinder associated with the second plate cylinder, the second blanket cylinder being mechanically coupled to said first blanket cylinder, a first drive motor for individually driving the first plate cylinder, a second drive motor for individually driving the second plate cylinder and a third drive motor for driving said first and second blanket cylinders, wherein the first and second printing units are printing a colored image on both sides of a running paper web. Although this embodiment of a printing unit arrangement according to the present invention involves a more sophisticated control system for controlling the three motors of the second printing unit compared to the one described herein before, it, at the same time, provides for a much higher flexibility with respect to the pagination of a print job which is run on the printing press, because the possibility of a flying imprinter operation on both sides of the running paper web does not require a pre-selection and cumulation of specific pages of print jobs which are associated with the flying imprinter operation in the pre-press stage.
According to an exemplary embodiment of the invention, the print unit arrangement further comprises a third printing unit, the third printing unit including a first plate cylinder, a first blanket cylinder associated with the first plate cylinder, a second plate cylinder, a second blanket cylinder associated with the second plate cylinder, the second blanket cylinder being mechanically coupled to the first blanket cylinder, a first drive motor for individually driving the first plate cylinder, a second drive motor for individually driving the second plate cylinder and a third drive motor for driving the first and second blanket cylinders.